The long term goal of my research program is to identify and examine the regulation of the genetic elements of DNA tumor virus genomes and use this knowledge to understand the mechanism(s) of eukaryotic gene expression and virus-host cell interaction. The immediate objective of the work proposed in this application is to study adenovirus gene expression using a molecular genetic approach. The following aspects of adenovirus gene expression will be studied: (1) Host range deletion mutants of Ad3 and 12 will be constructed using the 293 cell line as a complementing system. Possibility of using these host range mutants as trans-complementing helper viruses to generate defective deletion and point mutations in different regions of the Ad5 chromosome will be examined. (2) My present work on the structure and biological function of viral associated RNAs will be continued on the following lines-point and deletion mutations will be generated in VA RNA genes by cloning them on plasmids and by site directed mutagenesis. These mutations will re reintroduced into the virus, with or without helper viruses, to study their physiological consequences. The nucleotide sequences of the VA RNA genes of Ad3 and 12 will be determined. Any sequence homology that may be critical to VA RNA functions will be identified. (3) The biological function of early region 4 of Ad5 will be studied by isolating conditional lethal and deletion mutants. Physiological consequences of these mutations on transcription of other early genes and DNA synthesis will be studied. (4) The physiological significance of the "early" and "late" promoters of the messages from early region 2, coding for DNA binding proteins, will be examined by a genetic approach. Deletion mutations will be introduced into these promoters. The effect of these mutations on viral growth and transformation will be studied.